Sealing rings that comprise a U cup which retain an expander ring within a cavity are well known in the prior art. The sealing edges on such sealing rings extend sidewards from lips at the top of the U cup and are contracted by members to be sealed to deform the expander ring thereby loading the seal. The edges are disposed near the top of the U cup above the horizontal centerline of the expander ring when the expander ring is inserted in the cavity.
The loading of the sealing edges in the prior arrangement rotates the lip inner top portions into the expander ring thereby increasing the distortion or deformation of the expander ring at the area of contact with the lip portions. It is believed that this distortion results in the resistance forces of the expander ring being concentrated at the area of distortion in opposition to the rotation of the lip portions, thereby further increasing the fatigue failure at such location over the life of the expander ring.